74 lines
2.4 KiB
Java
74 lines
2.4 KiB
Java
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/*
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* Copyright (C) 2021 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package android.util.apk;
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import android.system.ErrnoException;
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import android.system.Os;
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import java.io.FileDescriptor;
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import java.io.IOException;
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import java.nio.ByteBuffer;
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import java.security.DigestException;
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/**
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* {@link DataSource} which provides data from a file descriptor by reading the sections
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* of the file via raw read() syscall. This is slower than memory-mapping but safer.
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*/
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class ReadFileDataSource implements DataSource {
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private final FileDescriptor mFd;
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private final long mFilePosition;
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private final long mSize;
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private static final int CHUNK_SIZE = 1024 * 1024;
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/**
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* Constructs a new {@code ReadFileDataSource} for the specified region of the file.
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*
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* @param fd file descriptor to read from.
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* @param position start position of the region in the file.
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* @param size size (in bytes) of the region.
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*/
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ReadFileDataSource(FileDescriptor fd, long position, long size) {
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mFd = fd;
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mFilePosition = position;
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mSize = size;
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}
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@Override
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public long size() {
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return mSize;
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}
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@Override
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public void feedIntoDataDigester(DataDigester md, long offset, int size)
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throws IOException, DigestException {
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try {
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final byte[] buffer = new byte[Math.min(size, CHUNK_SIZE)];
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final long start = mFilePosition + offset;
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final long end = start + size;
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for (long pos = start, curSize = Math.min(size, CHUNK_SIZE);
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pos < end; curSize = Math.min(end - pos, CHUNK_SIZE)) {
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final int readSize = Os.pread(mFd, buffer, 0, (int) curSize, pos);
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md.consume(ByteBuffer.wrap(buffer, 0, readSize));
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pos += readSize;
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}
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} catch (ErrnoException e) {
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throw new IOException(e);
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}
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}
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}
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